In related arts, there is a deduplication technique (a technique that eliminates a duplication) which detects identical data among a plurality of data in a storage, leaves one master data among a plurality of identical data and removes other data, and manages data with a reference to the master data and the number of references to the master data.
As a related technique, for example, there is a technique in which related information to be provided is determined by excluding duplicated information of delivered information or highly likely duplicated information of delivered information, among candidate information which may be provided as related information. There is another technique in which, in search of a neighborhood case for similar reference cases, a search order is determined by sorting the reference cases. When the neighborhood case is to be searched for the first reference case, search cases existing near the first reference case are stored in a cache. Then the neighborhood case is searched for from among the stored search cases. Further, there is a technique in which a tree-structured index is sequentially traced from a root node by referring to management information when a reference point is input to update the management information. The management information stores therein a set of a pointer to a node of the tree-structured index and a distance evaluation value between the reference point and a point corresponding to the node in a multi-dimensional vector space.
Related techniques are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2006-331014, Japanese Laid-Open Patent Publication No. 2004-326636 and Japanese Laid-Open Patent Publication No. 10-301937.